CVE-2023-23524: Apple iPadOS DoS Vulnerability

CVE-2023-23524 Overview

CVE-2023-23524 is a denial-of-service vulnerability affecting multiple Apple operating systems, including iOS, iPadOS, macOS Ventura, tvOS, and watchOS. The vulnerability stems from improper input validation when processing certificates. An attacker can exploit this flaw by crafting a malicious certificate that, when processed by a vulnerable Apple device, causes a denial-of-service condition.

This vulnerability was addressed by Apple through improved input validation in the certificate processing functionality. The flaw allows remote attackers to disrupt service availability without requiring any user interaction or authentication, making it particularly concerning for enterprise environments with multiple Apple devices.

Critical Impact

Remote attackers can cause denial-of-service conditions across Apple devices by sending maliciously crafted certificates, potentially disrupting business operations and device availability.

Affected Products

• Apple iOS versions prior to 16.3.1
• Apple iPadOS versions prior to 16.3.1
• Apple macOS Ventura versions prior to 13.2.1
• Apple tvOS versions prior to 16.3.2
• Apple watchOS versions prior to 9.3.1

Discovery Timeline

• February 27, 2023 - CVE-2023-23524 published to NVD
• March 18, 2025 - Last updated in NVD database

Technical Details for CVE-2023-23524

Vulnerability Analysis

CVE-2023-23524 is classified as CWE-400 (Uncontrolled Resource Consumption), indicating that the vulnerability allows attackers to exhaust system resources through improper handling of input data. The certificate processing component in affected Apple operating systems fails to properly validate certificate data before processing, allowing specially crafted certificates to trigger excessive resource consumption or processing errors that result in a denial-of-service condition.

The vulnerability can be exploited remotely over the network without requiring any user interaction or prior authentication. When a vulnerable device attempts to process a maliciously crafted certificate—potentially received through various network communications including web browsing, email, or application connections—the improper validation logic causes the device to enter an unrecoverable state or become unresponsive.

Root Cause

The root cause of this vulnerability is insufficient input validation in the certificate parsing and processing routines within Apple's security framework. When handling X.509 certificates, the affected components did not adequately verify the structure, length, or content of certificate fields before attempting to process them. This lack of boundary checking and input sanitization allows malformed certificate data to trigger unexpected behavior in the processing logic.

Attack Vector

This vulnerability can be exploited through network-based attack vectors where an attacker delivers a maliciously crafted certificate to a target device. Potential attack scenarios include:

The attack can be delivered through multiple channels where certificate validation occurs, such as:

• Establishing TLS/SSL connections with a malicious server presenting the crafted certificate
• Processing S/MIME signed or encrypted email messages
• Handling certificates embedded in various document formats
• Any application or service that triggers certificate validation

The attack requires no authentication and no user interaction beyond normal device operation, making it highly accessible to potential attackers. The impact is limited to availability, with no direct effect on confidentiality or integrity.

Detection Methods for CVE-2023-23524

Indicators of Compromise

• Unexpected device crashes or reboots during network communications
• System logs showing certificate processing failures or errors
• Devices becoming unresponsive when connecting to specific network resources
• Repeated crashes in security-related system processes

Detection Strategies

• Monitor system logs for certificate validation failures and crashes in security services
• Implement network-level inspection for malformed certificates in TLS handshakes
• Deploy endpoint detection solutions capable of identifying abnormal certificate processing behavior
• Track unusual patterns of device restarts or service interruptions across Apple devices

Monitoring Recommendations

• Enable comprehensive logging on Apple devices to capture certificate processing events
• Implement network traffic analysis to identify potential malicious certificate delivery attempts
• Establish baseline behavior for device stability to detect anomalous crash patterns
• Configure alerting for repeated certificate validation failures from specific sources

How to Mitigate CVE-2023-23524

Immediate Actions Required

• Update all affected Apple devices to the patched versions immediately
• Prioritize updating devices with network exposure or those handling sensitive communications
• Implement network-level protections to filter potentially malicious certificate traffic
• Review and audit certificate sources trusted by your organization

Patch Information

Apple has released security updates that address this vulnerability through improved input validation. Organizations should apply the following updates:

• iOS and iPadOS: Update to version 16.3.1 or later - See Apple Security Advisory HT213635
• macOS Ventura: Update to version 13.2.1 or later - See Apple Security Advisory HT213633
• tvOS: Update to version 16.3.2 or later - See Apple Security Advisory HT213632
• watchOS: Update to version 9.3.1 or later - See Apple Security Advisory HT213634

Workarounds

• Limit network exposure of unpatched devices by restricting internet connectivity
• Implement network-level certificate inspection and filtering where possible
• Use mobile device management (MDM) solutions to enforce update policies and restrict access to untrusted networks
• Consider network segmentation to isolate vulnerable devices until patches can be applied